1. Field of the Invention
The present invention relates to timing measurement of signals in PICA (picosecond imaging circuit analysis) systems, and particularly to methods and apparatus for timing measurement and calibration of timing measurement.
2. Prior Art
New package types, shrinking process geometries and new material pose challenges for gathering vital timing measurement during the integrated circuit (IC) design debug and validation process. Increasingly sensitive devices are easily perturbed during probing, which skews results and slows the design process.
Fault localization methods using beam probe systems are time-consuming even with access to IC layout knowledge since each node must be probed serially to trace the location of a faulty circuit element. Tester and other equipment time is often limited, forcing design debug experts to extract timing measurements from the device one probing session at a time, often adding weeks to the debug and verification cycle.
Timing data acquisition and analysis can be a development bottleneck. With conventional serial probe systems, skilled IC diagnostic experts are required to analyze the critical device data to know which node to probe next. Though companies often develop multiple products simultaneously, data acquisition, review and analysis capabilities are available only at the probe system's site. If a single node is missed, a new probe session must be set up, effectively limiting progress to one device at a time.
Silicon on insulator (SOI) technology offers increased power capabilities and device performance, but its sensitive structure requires non-invasive probing. Devices manufactured with 0.13-micron geometry have critical signal nodes so small and numerous that the acquisition process is too time-consuming for efficient probe by serial, beam-based instruments.
Picosecond Imaging Circuit Analysis (PICA) technology developed by IBM uses naturally occurring light emission from stimulated CMOS transistors to extract timing measurements and localize faults. Detecting the emitted light with high-speed optical detectors allows circuit switching to be monitored. By imaging and time-resolving light emission from many devices on an operating chip, the flow of information through the chip can be displayed as a movie.
More details of PICA methods and systems are found in the following documents which are incorporated herein by this reference: U.S. Pat. No. 5,940,545 dated Aug. 17, 1999, Kash et al., Noninvasive Optical Method for Measuring Internal Switching and Other Dynamic Parameters of CMOS Circuits; U.S. Pat. No. 6,028,952 dated Feb. 22, 2000, Kash et al., System and Method for Compressing and Analyzing Time-Resolved Optical Data Obtained from Operating Integrated Circuits; U.S. Pat. No. 6,172,512 dated Jan. 9, 2001, Evans et al., Image Processing Methods for the Optical Detection of Dynamic Errors in Integrated Circuits; U.S. Pat. No. 6,304,668 (withdrawn) dated Oct. 16, 2001, Evans et al., Using Time Resolved Light Emission from VLSI Circuit Devices for Navigation on Complex Systems; European patent publication EP 0 937 989 published 25 Aug. 1999, Evans et al., IBM, Using Time Resolved Light Emission from VLSI Circuit Devices for Navigation on Complex Systems; J. BUDE, Hot-carrier luminescence in Si, PHYS. REV. B, 45(11), 15 Mar. 1992, pages 5848–5856; S. VILLA et al., Photon emission from hot electrons in silicon, PHYS. REV. B, 52(15), 15 Oct. 1995-I, pages 10993–10999; J. KASH et al., Full Chip Optical Imaging of Logic State Evolution in CMOS Circuits, IEDM 96 Late News Paper (1996) 1, pages 934–936; D. KNEBEL et al., Diagnosis and Characterization of Timing-Related Defects by Time-Dependent Light Emission, ITC PROCEEDINGS 1998; M. BRUCE et al., Waveform Acquisition from the Backside of Silicon Using Electro-Optic Probing, PROCEEDINGS FROM THE 25th INTERNATIONAL SYMPOSIUM FOR TESTING AND FAILURE ANALYSIS, 14–18 Nov. 1999, pages 19–25; T. EILES et al., Optical Probing of VLSI IC's from the Silicon Backside, Proceedings from the 25th International Symposium for Testing and Failure Analysis, 14–18 Nov. 1999, pages 27–33, and M. MCMANUS, Picosecond Imaging Circuit Analysis of the IBM G6 Microprocessor Cache, PROCEEDINGS FROM THE 25th INTERNATIONAL SYMPOSIUM FOR TESTING AND FAILURE ANALYSIS, 14–18 Nov. 1999, pages 35–38.
Precise time resolution of the detected photons is important in electro-optic probing. Suitable high-resolution timing measurement methods and apparatus are desired, along with methods for their calibration.